Apparatus for electrolytically treating the interior of a bore



B. A. SCHWARTZ, JR 3,183,176

Ma)r 11, 1965 APPARATUS FOR ELECTROLYTICALLY TREATING THE INTERIOR 0F ABORE Filed July 28, 1960 3 Sheets-Sheet l May 11, 1965 B. A. scHwARTz,JR 3,183,175

APPARATUS FOR ELECTROLYTICALLY TREATING THE INTERIOR OF A BORE FiledJuly 28. 1960 s sheets-sheet 2 BY 5m M,

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May 11, 1965 a. A. scHwARTz, JR 3,183,176

APPARATUS FOR ELECTROLYTICALLY TREA'I'INGl THE INTERIOR OF A BRE FiledJuly 28, 1960 3 Sheets-Sheet 3 f oooooooo-/Q *wie INVENTOR.

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BY l Qn-Q United States Patent (l) 3,183,176 APPARATUS FORELECTROLYTICALLY TREAT- EWG THE INTERIR F A BORE Benno A. Schwartz, Jr.,Cleveland, Ohio, assigner, by mesne assignments, to The SteelImprovement and ll-ge Company, Cleveland, hio, a corporation of FiledJuly 28, 1960, Ser. No. 45,921 Claims. (Cl. 20d- 212) This inventionrelates to a method and apparatus, and products thereof, forelectrocleaning and electroplating, and more particularly to a methodand apparatus for automatically carrying out electrolytic cleaning andelectroplating operations of the type in which the surface to be platedis subjected to a rubbing or brushing action as the -electrolytic actiontakes place, and to the products of the method and apparatus.

-Electrolytic cleaning and plating opeartions in which an electrodehaving a porous surface that is saturated with electrolyte is rubbedover the surface to be cleaned yor plated, are well known and are Widelyand successfully used. Diliiculties have arisen with such methods inwhich hand tools are employed, however, because of non-uniformity ofresults, the cost of the labor that is involved and the impracticabilityof plating within cylindrical open-ings or passageways.

A general object of the present invention, therefore, is the provisionof a method and apparatus whereby electrolytic cleaning andelectroplating operations can be carried out by machine eiciently and atlow cost. Another object is the provision of a method and apparatusparticularly adapted to electrolcleaning and electroplating the interiorsurface of cylinders, bores, drilled openings and the like. Anotherobject is the provision of an apparatus for subjecting the interiorsurfaces of bores and the like to simultaneous electrolytic andscrubbing actions. A further object is the provision of such anapparatus which can be manufactured at reasonable cost, which isreliable and eiiicient in operation and which produces uniform resultson the interior surface of the bore. A further object is the provisionof a method for electrolytic treat-ment of internal bores and the likewhich will assure simultaneous and uniform rubbing of the surface to betreated while the electrolytic operation is carried out.

Another object is the provision of a method of electroplating wherebydense, high quality deposits can be obtained at high rates ofdeposition. Another object is the provision of a method and apparatuswhereby a levelling or smoothing effect is obtained during the platingoperation with electrolytes that are not capable of producing thiseiiect with conventional procedures. Another object is the provision ofa method of producing high quality electro-deposited coatings ofchromium and alloysthercof. Another object is the provision of adherent,dense and unusually smooth electro-deposited metallic coatings. Furtherobjects and advantages of the invention will become apparent from thefollowing description of a preferred form thereof, reference being madeto the accompany-ing drawings in which: l

FIGURE 1 is a somewhat diagrammatic, isometric View illustrating anapparatus embodying a preferred form of my invention;

FIGURE 2 is a front elevational View, partly in section and on anenlarged scale, of a portion of the apparatus shown in FIGURE l;

FIGURE 3 is an elevaitonal view, with parts broken away, of theelectrode tool utilized in the apparatus, showing it removed from theapparatus;

FIGURE 4 is a bottom view of the tool, taken as indicated by line 4 4 ofFIGURE l;

3,183,175 Patented May 11, 1965 IFIGURES 5 and 6 are horizontal sectionstaken along lines :i--S and 6-6 of FIGURE 3 respectively; and

FIGURE 7 is a horizontal sectional view taken as indicated by line 7-7of FIGURE 3, but showing the tool in the position it takes when it isinserted in a bore to be treated.

Brieiiy, according to a preferred form of the invention electrolytictreatment of metal surfaces is carried out by making the part to betreated one electrode of the electrolytic system while the otherelectrode is constituted by an electrically conductive tool having aporous dielectric surface that is brought into contact with the surfaceto be treated and supplied with electrolyte while the tool and thesurface are moved rapidly relative to each other, preferably in aplurality of directions. In the case of bores or other surfaces ofrevolution, the movements preferably consist in rotation about the axisof the surface and simultaneous reciprocation in a direction parallel tothe axis of the surface. By this means all parts of the surface to betreated receive substantially equal treatment, and thus the surface canbe uniformly cleaned and/ or electroplated. The rapid rubbing actionmakes possible production of uniform, high-quality deposits at highrates of deposition in electroplating operations and has an unexpectedresult in that the plating operation can be carried out so that thedeposited coatings are given a bright, burnished or satiny appearance bythe plating operation itself and Without requiring buiiing or polishing.The circulation of the electrolyte insures that fresh electrolyte isalways present at the surface. The result is that the operation can becarried out rapidly and economically and produces results of uniformlyhigh quality. The method employed makes possible the rapid production ofelectro-deposited coatings that are highly adherent to the underlyingsurface and that are exceptionally hard, dense and smoot The apparatusfor carrying out the method consists of a hollow, electricallyconductive tool having a porous surface for enga-ging the work andthrough which the electrolyte is caused to flo-w, and means for movingthe porous surface rapidly with respect to the surface being treated.This means, in the preferred form of the invention disclosed herein,takes the form of a tool mounted in a conventional drill press modifiedslightly to enable it automaically to carry out the desired functions.The drill press provides a simple, economical and reliable machine forimparting the required motions to the tool. Preferably, the desiredrubbing froce is obtained by the action of centrifugal force on parts ofthe tool. Thus, the tool can be made of extremely simple construction aswill appear below. All that is necessary, then, to enable the operationto be carried out is an appropriate source of electric power, which maybe of conventional construction, and a simple pump and fluid system forcirculating the electrolyte through the tool.

Referring to FIGURE l, the drill press which forms the basis for theapparatus is indicated in general at 10. The press is of conventionalconstruction and typically may comprise a base 11, a pedestal 12 whichsupports aV bed plate 13 and a bracket 14. The bracket carries a spindlel5 which supports a convention-al chuck 16. As appears below, the toolor electrode indicated in general at 18, issupported bythe chuck. Thespindle is rotated at the desired speed by means of a motor 19 whichdrives the spindle through a belt 20 in a conventional manner.

As will appear in greater detail below, electrolyte is pumped from asump or storage tank 22 by a small motor-driven pump 23 through conduits24 to the tool 18. The electrolyte flows outwardlylthrough the porous,dielectric surface of the tool into contact with the inner surface ofthe bore in the work W and then falls by gravity into the sump 22.

aree,

In order to prevent the electrolyte from splattering and to protect thepress from corrosion, the work is preferably surrounded by a shield 26which may be composed of a transparent plastic. A perforated plasticshield 27 (see FIGURE 2) is also interposed between the work and the bed13 of the drill press. The bed of the press also has openings through itand thus the electrolyte can run out of the work through the plasticshield 27 and the bed into the sump 22. Preferably, the electrolyte ispassed through a filter 28 before it is returned to the Work.

The electric power supply to the plating electrode and the work ispreferably conventional and preferably consists of a conventional D.C.supply 30 that is connected to the tool by conductor 311, clamp 32 andconductor 33, and to the work by conductor 35 and clamp 36. rThe powersupply 30 contains the usual controls and meters, so that the voltageand current density can be controlled to produce the desired results.When the apparatus is used for plating, the tool 18 is made the anodeand the Work the cathode; when the apparatus is used for electrolyticcleaning, the polarity is ordinarily reversed, the work being made theanode.

In order to impart the preferred reciprocatory motion to the electrodetool 18, the spindle advancing and retracting mechanism of the drillpress 1t) is employed. In a conventional press such as shown herein thismechanism embodies a rack and pinion or like mechanism which is`actuated by a manually operated handle. The modification of the drillpress to suit the purposes of the present invention requires that theconventional handle be removed and a pinion 3S substituted therefor.Pinion 38 is engaged by a rack 39 which is connected to a piston rod 40attached to piston 41 operating in cylinder 42. The cylinder 42 may besupported from pedestal 12 by any convenient bracket 44.

The piston 41 is caused to reciprocate within the cylinder 42 and thusto reciprocate the rack 39 and move the spindle up and down byalternately connecting the opposite ends of the cylinder to a source ofiiuid, such as air, under pressure and to a discharge port. This may becarried out by means of a conventional solenoid-operated four-way orreversing valve 45 which is connected to the opposite ends of thecylinder by means Vof conduits 46 and 47, and to a compressor 4S orother source of fluid under pressure by conduits 49. The valve may be ofconventional construction and per se forms no part of the presentinvention. The valve is controlled by a solenoid Si). The speed ofreciprocation of the cylinder may be controlled by a flow control orpressure regulating Valve 51 interposed in the line leading to thecompressor.

In order to reverse the operation of the piston, a dog S3 is mounted ona bracket 54 carried by the piston rod 40. The dog is adapted to engagethe actuating plungers of limit switches 55 and 56. The limit switchesare arranged to control the operation of solenoid valve 45 throughconventional electrical circuits 57 and 58. When the dog 53 engages theswitch 55, the connections through the valve d are reversed so thatfluid under pressure, which theretofore had been supplied throughconduit 46, is then supplied through conduit 47 while conduit 46 isconnected to atmosphere. When the piston reaches the other end of thestroke, dog 53 engages switch 56 and again reverses the connections sothat conduit 46 is connected to the pump and conduit 47 to atmospherestarting the motion of the piston 41 over again in its originaldirection.

In order to control the length of the stroke, the limit switches 55 and56 are adjustably mounted in any convenient manner, for example, on amounting plate 59, the switches being clamped to the plate in thedesired positions of adjustment by clamping screws (not shown) extendingthrough the slots 59a and 5% in the mounting plates.

The apparatus described above functions to rotate and reciprocate in thetool 18. The power supply 30 sup- Iplies the required electrical energyto the tool and the work, and the pump 23 and associated parts supplythe electrolyte to the tool.

As shown particularly in FIGURES 3 to 7, the tool 1S is constructed upona tube 66 which is closed at both ends by plugs 61. The tube is clampedin the chuck 16 of the drill press and thus supports the entire tool. Inorder to supply electrolyte to the interior of the tool, a stationarycollar 62 is mounted on the tube 6i), the collar having a counterborerecess 63 therein and openings 64 to which the conduits 24 leading fromthe pump 23 are connected. The tube 60 is provided with perforations 65in the zone Within the counter bored portion 63 so that fluid enteringthe openings 64 can flow into the interior of the tube 60. The conductor33, which is rigid, also is threaded into the collar 62. This serves tohold the collar 62 against rotation and allow it to supply electricpower thereto.

In order to position the collar 62 on the tube 60, rings 66 and 67 arepositioned above and below the collar 62 on the tube. These make pressfits on the tube which are sufficient to prevent substantial leakage ofelectrolyte along the tube since the pressure of the electrolyte isrelatively low; the rings are held in place by means of set screws.Leakage between the rings 66 and 67, which rotate with the tube 69, andthe stationary collars 62 is prevented by rubber packing members 68 and69.

The work engaging portions of the tool are supported beneath thestationary collar 62 by means of rings 71 and 72 that are secured to thetube 60 by appropriate set screws. These rings pivotally support arcuatework engaging varies 73; the vanes are provided with pivot pins 75 attheir opposite ends which engage within recesses 76 in the rings 71 and72 as shown particularly in FIGURE 3.

Since the tool 18 acts as an electrode, the tube 60, collar 62, rings 66and 67, rings 71 and 72, and vanes 73 are all made of conductivematerial. Preferably, all parts of the electrode tool are composed ofmaterials that are inert to the electrolyte. Stainless steel issatisfactory for the conductive parts for many services and is used inthe preferred form of tool illustrated herein. For other servicesplatinum-activated titanium may be required, in other instances carbonor graphite may be found to be satisfactory.

In order to provide a porous dielectric surface on the vanes 73 forengagement with the work, the vanes are each covered with a layer ofporous dielectric material 73. The material may consist of anyappropriate electrolyte-permeable dielectric material that will not beattacked by the electrolyte and that will not contaminate theelectrolyte. lFelt is satisfactory, but I prefer to employ a perforatedplastic material consisting of sheet of nylon about 0.031 in thickness,having about 70 perforations per square inch, the perforations beingabout 3/2" in diameter. This material has better wearing qualities thanfeit. The material is held in place by arcuate clamping members 79 whichare secured to the vanes 73 by means of screws S0. It is to be notedthat the vanes, which act as anodes in plating operations, are spacedfrom the surface to be plated by the thickness of the dielectricmaterial.

'In order to provide for the iiow of electrolyte into and through thedielectric surfaces that engage the work, the tube 60 is perforated asshown at 82 in the zone between the rings 71 and 72 and the varies 73are provided with passages 83 which permit the electrolyte to ilow tothe inner surfaces of the porous dielectric covers 78. If desired,grooves 84 may be provided in the outer faces of the varies in order todistribute the electrolyte more uniformly. These grooves oridinarily arenot essential, however.

In practice, the diameter of the tool with the vanes 73 in the positionshown in FIGURE 7 is only slightly less than the diameter of the bore tobe plated. 'I'he tool is inserted in the bore with the vanes in theposition shown in FIGURE 7 g when the tool is rotated in the directionindicated the vanes each swing outwardly a few degrees under the inuenceof centrifugal force and also under the iniiuence of the pressure of theelectrolyte in the space within the varies. The electrolyte flowsthrough the passages 83 and is distributed by the porous dielectriccovers '78 throughout substantially the entire outer area of each vane.

The speed of rotation of the tool is such that the speed at which thedielectlic surfaces rub the work is large as compared to the rubbingspeed ordinarily employed or possible in brush plating with hand tools.For example, in plating a bore having an internal diameter oi an inchand a quarter, I have obtained excellent results by rotating the tool ata speed of 1280 rpm. This gives a rubbing speed of a little over 5,000inches per minute or about 84 inches per second. 'Ilhe rubbing speed of84 inches per second is much greater than the rubbing speed ordinarilyemployed in brush plating operations, which usually is about two orthree inches per second and rarely exceeds inches per second when brushplating with hand tools.

Although I have not been able to measure the pressure exerted by thevanes on the Work, calculations indicate that the pressure of the vanesagainst the work is of the order of about three to about :live poundsper square inch at the speeds ordinarily employed. This pressureincreases if the rotational speed of the tool is increased and decreasesif the rotational speed is decreased.

According to the present invention, the increased rubbing speed isaccompanied by replenishment of electrolyte at the surface to be platedat a much greater rate than is normally employed in brush plating.Conventional brush plating operations are carried out by simply dippinga porous electrode into an electrolyte and then applying it to the work,the electrolyte being replenished every few seconds by redipping thetool in the electrolyte. As distinguished from this, in plating a boreabout 1.2 inches in diameter and about 2 inches long according to thepresent invention, electrolyte is pumped through the tool at the rate ofone half gallon to one gallon of electrolyte per minute, i.e., about 9to 18 gallons of electrolyte per minute per square foot of sur-facebeing plated. While the electrolyte is circulated in this manner, thetool is rotated at 1280 r.p.m. as noted above and reciprocated at therate of sixty one quarter inch strokes per minute, the rotation andreciprocation of the tool, coupled with the preferred staggeredarrangement of the perforations in the dielectric integument coveringthe vanes 73 insures the continuous replenishment of the electrolyteover all of the surface being plated at all times during the platingoperation, while the rubbing action physically removes gases andunwanted impurities and other precipitates from the surface to be platedand probably the cathode lm is physically disturbed. The impurities andprecipitates are carried oif with the electrolyte that flows out throughthe bottom of the bore and into the sump in the example given and areremoved by iiltering the electrolyte. The gases are either carried awaywith the electrolyte or permitted to rise into the atmosphere. In anyevent,-it appears that the rubbing at high speed and the rapid rate ofcirculation of electrolyte insures that the electrolytic action takesplace on surfaces that are maintained in clean condition andsubstantially free from gas and with electrolyte that is in goedcondition.

It is also probable that the rapid and alternate wiping of the surfaceto be plated and replenishment of the electrolyte brought about by t-hetool contributes materially to the success of the present invention. Inthe example given, with about 70 openings per square inch in theinteguments 78 there are slightly more than eight alternate lands orrubbing areas and perforations for each lineal inch of the surface ofthe dielectric material 78. Thus, with the tool rotating at a speed of1280 r.p.m. and t-he rubbing speed of the dielectric material on thework being a little more than 84 inches per second, we iind that as thetool traverses the work the surface of the work is alternately subjectedto the rubbing or wiping action of the lands and then replenished withthe electrolyte flowing through the perforations at a very highfrequency-of the order of 650 or more times per second. As each rubbingelement or land of the dielectric material passes over the surface, itat least partially sweeps away and disturbs the thin film ofelectrolyte, known as the cathode iilm, immediately adjacent the surfaceand then the electrolyte is immediately replenished by electrolyteflowing through the perfor-ations. The mechanical action of the toolseems to insure the removal of unwanted products of the electrolysiswhile the circulation of the electrolyte insures that fresh electrolyteis always available to replenish the electrolyte that is mechanicallyswept away. Carrying out these operations at high speed appears to beone of the factors that gives unexpectedly advantageous results in thecharacter of films deposited according to my process. The character ofthe deposit in terms of density and smoothness can also be varied byvarying the speed of rotation of the tool. In general, for a givencurrent density, higher rotational speeds increase the smoothness anddensity of the deposits, but unexpectedly, by use of high currentdensities and high rubbing speeds (which results in increased rubbingpressure) it is possible to produce deposits that are porous yet smoothas compared to ordinary porous deposits.

Regardless of the reasons, the results obtained by the use of thepresent invention are unique and remarkably advantageous; and, so far asI am aware, have not been possible of attainment heretofore. Typicalexamples are given below.

Example 1.-A cast iron bore havin-g an internal diameter or" about 1.2inches was subjected to the following conventional preliminaryoperations.

(1) Degreasing in a solvent degreasing solution.

(2) Anodic degreasing in a solution of sodium hydroxide.

(3) Anodic etching for live seconds using a solution of hydrochloricacid with a hand brush plating tool at 13 volts.

(4) Flash plating with a conventional nickel brush plating solution toprovide a nickel coating of approximately 000005 using a conventionalbrush plating tool for approximately 10 seconds.

Thereafter, the bore was plated according to the present invention usingthe tool previously described. rlibe to-ol Was rotated at a speed of1280 rpm. and reciprocated for a distance of about 1A at the rate ofapproximately 60 strokes per minute. The plating was carried out byusing the following conventional copper cyanide electrolyte.

Grams Copper cyanide 124 Sodium cyanide Sodium hydroxide 6.25

Water, -to make one liter.

Using a current of 50 amperes at 14 volts, a bore having an area ofabout 7 square inches was plated with copper to a thickness of .001 inchin 50 seconds. The average current density was slightly in excess of1,000 amperes per square foot. The deposit was dense, adherent andsmooth and presented a burnished or polished appearance. Even higherrates of deposition with excellent results can be obtained by usingproprietary brush plating electrolytes, the composition of which is notknown tome, although they are, I believe, electrolytes of the generaltype set forth above with special additives to make possible increasedrates of deposition. YFor example, I have deposited copper under thesame condition except for increased current densities at rates of from.0010 to .0015 inch in -thirty seconds, using a proprietary copperplating solution. This rate is much greater than can be attained by handbrush plating operations with the same electrolyte, just as the ratewith the conventional cyanide electrolyte set forth above is muchgreater than can be attained in ordinary bath plating. Also, thecharacter of the plated deposit is superior from the standpoint ofdensity, adherence and smooth, shiny appearance.

So far as I am aware, any plating solution that is suitable for use in ahand brush plating operation may be used with advantageous andunexpectedly better results according to the present invention.

The method and apparatus of the invention have given especially usefulresults in the production of very hard chromium iron alloy deposits. Anaqueous electrolyte of the following composition was employed:

Ammonium hydroxide [28% -NH4OH] -ml./l 60 Chromium ammonium sulfate[Cr2(SO4)3 (NH4)2SO4 24H20] -g./l 700.0 Ferrous ammonium sulfate g./1.Magnesium sulfate [MgSO4-7H2G] --g./l- 25.0 Ammonium sulfate [(NHQZSOQg./l 50.0

This bath is disclosed as Example I in the Snavely et al. Patent No.2,693,444, except that in Example I in the patent the magnesium sulfatecontent of the bath is 20 grams per liter and the bath also includessmall amount of sodium sultite, which was not used in the electrolyteemployed in my tests.

Example I1.-In one test, the surface of a bore in cast iron, which hadbeen given the same preliminary treatment set forth in Example I above,including a flash of nickel, was subjected to a plating operation at therotational speed and rate of reciprocation given above with acirculation of one-half gallon of the above chromiumiron electrolyte perminute. The bath temperature was 149 F. The current was 80 amperes andthe average current density was 1650 amperes per square foot. Theplating operation was carried out for a period of ten minutes. Thethickness of the plate was .0005 indicating a plating rate of .0030" perhour. The deposit was adherent uniform, light and satiny in the areawhich had been subjected to the brushing action of the tool. In areas ofthe bore that Were not subjected to the action of the tool, the coatingwas loose and black.

Example IIL-In another test, the preliminary treatment, electrolyte,work piece and speed of rotation and Ieciprocation of the tool were thesame as in Example II. The bath temperature was 149 F.; the currentdensity was 50 amperes, giving a current density of 1030 amperes persquare foot; the time of plating was l() minutes. This produced a platedcoating of .0002 indicating a plating rate of .0012" per hour. Thedeposit again was adherent, uniform and shiny in the area that wasbrushed by the tool and porous, dark and dull in the area that was notbrushed. In this example, as in the case of Example II, the plating wasvery hard.

Example IV.-In this test all the conditions were the same as in theExample III, except that the bath temperature was 144 F., the currentwas increased to 90 amperes giving an average current density of 1850amperes'per square foot and the plating operation was carried out fortive minutes. The thickness of the plating was .0017 inch indicating aplating rate of .020 inch per hour. The deposit was adherent, uniform,light and satiny in appearance throughout the area acted upon by thetool. The hardness tested with a Knoop tester and a l gram load gave anaverage of ,1034, which is equivalent to a Rockwell C hardness of 72.3.The hardness test was made with the indentation parallel to the surfaceof the plating.

Example V.-In another test, the internal surface of an aluminum tube wasfirst subjected to an anodic cleaning and etching operation with the useof a hand brush plating tool and a hydrochloric acid electrolyte asdisclosed in my copending application Serial No. 1,265, led March 4,1960, and then given a ash of nickel, by a conventional brush platingoperation with a hand tool. The bore was then plated with the apparatusof the present invention operating at a speed of 1280 r.p.m.,reciprocating at a rate of sixty one quarter inch strokes per minute andwith the above chromium-iron electrolyte circulated at the rate ofone-half gallon per minute. The bath temperature was 149 F., the currentwas 50 arnperes, the area plated 5.7 square inches, giving an averagecurrent density of 1260 amperes per square foot. The time of plating was30 minutes which produced a uniform, adherent, light and mirror-likecoating, having a thickness of .0011 inch, indicating a plating rate of.0022 per hour. Metallographic examination showed the structure to bedense with only occasional surface to base metal cracks. The averageKnoop hardness of the plating with indentation parallel to surface was955, equivalent to 69.2 on the Rockwell C scale. The hardness given intests of Examples IV and V is unexpectedly high, the hardness of thecoating ordinarily obtained by the method disclosed in the said Snavelyet al. patent ordinarily being 600 to 700 Knoop as recited in thepatent. The Rockwell C hardnesses of 72.3 and 69.2 compare with usualhardnesses of 45 to 55 on the Rockwell C scale obtained with the sametype electrolyte in a conventional plating bath.

Another unexpected result of the plating operation is a smoothness ofthe finish. As mentioned above, in all of the examples the plateddeposits presented remarkably smooth appearances; in some instances themetal as plated looks as though it had been burnished. Profilometertests were made of the aluminum tube plated in Example V. The surfaceroughness of the plated sample was 10-13 micro inches R.M.S. A similaraluminum tube subjected to the same etching procedure that was used inproducing the sample of the Example V had prior to plating a surfaceroughness of 35-45 micro inches RMS. Thus, the surface roughness wasgreatly reduced by the plating operation. This result is contrary toexpectation. Ordinarily, chromium plating follows closely the underlyingsurface and the roughness of the plated surface, as determined byprotilometer tests, corresponds quite closely to the roughness of thesurface prior to plating. The theory underlying the production of theunusually smooth surfaces is not known to me at present. However, itdoes not appear likely that the surface of the tool, which isnon-abrasive and relatively soft and which rubs the work rather lightly,could physically smooth out the metal once it has been deposited.Instead, it seems more probable that the tool, in some manner notpresently known to me, but which may result from the probable physicaldisturbance of the cathode film by the dielectric elements of the tool,causes the electrodeposition to take place in such a way that surfaceroughness is reduced and the desired smoothness and density is obtained.Another effect that I have observed is that the etieiency of the platingoperation is improved as compared with conventional methods; that is, agreater weight of metal is deposited per ampere hour with the presentinvention than with conventional procedures employing the sameelectrolyte.

In general, if the rotational speed of the tool is reducedsubstantially, the coated deposits do not present as shiny or asburnished an appearance as they do with the higher rotational Spee givenin the preferred example. However, for some purposes, such surfaces maybe desired and may be adequate, and speeds of the order of 400 r.p.m.,or about 1200 inches per minute lineal speed is entirely satisfactoryfor many purposes. Increased current density amare/e may increase theporosity and decrease the density of the deposits. In general, currentdensity and rate of deposition can be increased while maintaining thequality of the deposit if the rubbing speed and rate of circulation `ofthe electrolyte are increased. Again, these factors may be varied inaccordance with the character of the deposits required. The use of themethod and apparatus of the present invention, however, makes possiblethe rapid production of high-quality coatings and lends itselfparticularly to automatic coating lines and long production runs. Theapparatus may also be utilized for electrolytic cleaning and etching,and in such uses where conventional electrolytes are employed, similaradvantages of uniformity and high speed of surface treatment areattained.

The chromium plating operation, which produces a strong, adherent,highly polished coating that probably is an alloy of about 94% chromiumand about 6% iron, is extremly advantageous not only from the standpointof the quality of the plating, but also because the trivalent chromiumbath employed docs not give olf the noxious fumes associated withconventional chromium baths. It is thus possible to carry out chromeplating operations without the use of hoods and without requiring theprecautions that are usually required in order to protect the workersfrom the health hazard that is present with ordinary chromium platingbaths.

The smoothness and density of the plated deposits is also of greatimportance. By the use ofthe present invention, bearing metals such aslead-tin alloys or lead-tinindium alloys can be plated directly in boresor on shafts if desired; aluminum cylinders and other parts as well asparts composed of other metals, can be provided with wear-resistantplatings of great hardness, and corrosion resistant deposits ofexcellent appearance can be produced.

lt appears probable that increasing the rubbing speed increases thepolishing, levelling or burnishing effect. Also, the higher the rubbingspeed, the higher the current density that can be employed with theproduction of dense adherent plating that presents a polished orburnished appearance. For a given electrolyte, there probably is aminimum speed below which the levelling, burnishing or polishing actiondoes not take place regardless of the current density employed, becausethis effect does not appear to be obtainable with hand brush platingtools.

The apparatus disclosed herein is intended particularly for the platingof bores. lt will be appreciated that machines of other types may bedevised which can be utilized to carry out the present method in theplating of external surfaces of revolution, fiat surfaces and surfacesof other shapes.

Those skilled in the art will appreciate that various changes andmodifications can be made in the invention without departing from thespirit and scope thereof. The essential characteristics are summarizedin the claims.

I claim:

1. Apparatus for electrolytically treating the interior of a bore in aworkpiece comprising a tool having a central spindle composed ofconductive material and adapted to be rotated, a vane composed ofconductive material and constituting an electrode mounted on saidspindle on a pivot parallel to and spaced from the axis of said spindle,a covering of porous dielectric material overlying said vane and adaptedto engage the interior surface of said bore, means for causingelectrolyte to flow through said porous covering into contact with theinterior surface of said bore, and means for rotating said electrodetool with respect to a workpiece.

2. Apparatus for electrolytically treating the interior of a bore in aworkpiece comprising a tool having a hollow central spindle adapted tobe rotated, a pair of vanes pivotally mounted on said spindle and havingsurfaces parallel to the axis yof said spindle, said vanes havingpassageways therethrough, said vanes and said spindle being composed ofconductive material, a covering of porous dielectric material overlyingeach of said vanes and adapted to engage the interior surface of a boreto be treated, means for supplying electrolyte to the interior of saidspindle, said spindle being perforated adjacent said vanes wherebyelectrolyte can flow through said porous covering and through said vanesand said covering into contact with the surface of the work, and meansfor rotating said electrode tool with respect to a workpiece.

3. Apparatus according to claim 2 wherein said porous covering comprisesa perforated integument composed of liexiole insulating material.

4. Apparatus for electrolytically treating the interior of a bore in aworkpiece comprising a tool having a hollow central spindle adapted tobe rotated, a pair of vanes composed of conductive material andconstituting electrodes pivotally mounted on said spindle and havingsurfaces parallel to the axis of said spindle and being adapted to swingoutwardly away from said spindle, said vanes having passagewaystherethrough, a covering of porous dielectric material overlying each ofsaid vanes and adapted to engage the interior surface of a bore to betreated, means for supplying electrolyte to the interior of saidspindle, said spindle being perforated adjacent said vanes wherebyelectrolyte can flow through said porous covering and through said vanesand said covering into contact with the surface of the work, and meansfor simultaneously rotating and reciprocating said electrode tool withrespect to a workpiece.

5. Apparatus according to claim 4 wherein said vanes are pivotedadjacent the edges thereof whereby the vanes tend to swing outwardlytoward said bore under the inuence of centrifugal force when said toolis rotated.

References Cited by the Examiner UNITED STATES PATENTS 2,419,190 4/ 47Wagoner 204--29 2,530,524 11/50 Hlavin 204-217 2,752,302 6/ 56 Magnus204-29 2,764,543 9/ 5 6 Comstock et al. 204-217 2,783,199 2/57 Comstock204-224 3,022,232 2/ 62 Bailey et al. 204--26 FOREIGN PATENTS 18,6438/00 Great Britain. of 1899 WINSTON A. DOUGLAS, Primary Examiner.

JOHN R. SPECK, MURRAY TILLMAN, JOSEPH REBOLD, Examiners.

1. APPARATUS FOR ELECTROLYTICALLY TREATING THE INTERIOR OF A BORE IN AWORKPIECE COMPRISING A TOOL HAVING A CENTRAL SPINDLE COMPOSED OFCONDUCTIVE MATERIAL AND ADAPTED TO BE ROTATED, A VANE COMPOSED OFCONDUCTIVE MATERIAL AND CONSTITUTING AN ELECTRODE MOUNTED ON SAIDSPINDLE ON A PIVOT PARALLEL TO AND SPACED FROM THE AXIS OF SAID SPINDLE,A COVERING OF POROUS DIELECTRIC MATERIAL OVERLYING SAID VANE AND ADAPTEDTO ENGAGE THE INTERIOR SURFACE OF SAID BORE, MEANS FOR CAUSINGELECTROLYTE TO FLOW THROUGH SAID POROUS COVERING INTO CONTACT WITH THEINTERIOR SURFACE OF SAID BORE, AND MEANS FOR ROTATING SAID ELECTRODETOOL WITH RESPECT TO A WORKPIECE.